Field of the Invention
The invention relates to an electricity storage battery, such as a redox flow battery.
Description of the Related Art
In the prior art, an electrolyte solution for use in an electricity storage battery is known to contain a metal redox material and a chelating agent (refer to Patent Document 1 and Non-Patent Document 1). Patent Document 1 discloses a cathode electrolyte solution containing a Mn redox material and a complexing agent or a chelating agent. Examples of the complexing or chelating agent described in Patent Document 1 are an aminopolycarboxylic acid, a carboxylic acid, an amino acid, an oxyacid, a polyalcohol, a β-diketone, an amine and a polyphosphoric acid. Patent Document 1 also discloses, in the columns of the examples, a cathode electrolyte solution that contains a manganese redox material and a chelating agent being pyrophosphoric acid, an ethylenediaminetetraacetate (EDTA) salt or a hydroxyethylenediaminetriacetate salt. Non-Patent Document 1 describes that a Mn(III)-EDTA complex (ethylenediaminetetraacetatomanganate(III) complex) may self-decompose with generation of CO2 gas.